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https://issues.apache.org/jira/browse/MATH-1413?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Rob Tompkins updated MATH-1413:
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Fix Version/s: 4.0
> Add generics to Frequency
> -------------------------
>
> Key: MATH-1413
> URL: https://issues.apache.org/jira/browse/MATH-1413
> Project: Commons Math
> Issue Type: Bug
> Reporter: Bruno P. Kinoshita
> Assignee: Bruno P. Kinoshita
> Priority: Minor
> Labels: generics
> Fix For: 4.0
>
>
> The Frequency class has no generic types, but creates an internal TreeMap,
> with keys with the type `Comparator<?>`. Then whenever you add or get values
> from the TreeMap, it will throw CCE if you pass a key value with a different
> type from the others stored in the map.
> {code}
> Frequency f = new Frequency();
> // Okay
> f.addValue("Ola");
> // Key 12, type Integer, does not match String type. CCE, wrapped in a Math
> exception
> f.addValue(12);
> {code}
> And even a simpler example without Math classes to help outlining the issue.
> {code}
> TreeMap<Integer, String> map = new TreeMap<>();
> int key = 1;
> map.put(key, "One");
> // Okay
> map.get(100);
> // TreeMap will try to call 1.1#compareTo against each Key it contains, which
> can result
> // in a CCE here.
> map.get(1.1);
> {code}
> It is not clear how we could compare the key type to the given v value.
> Checking if the map is not empty, and then checking the type of the first key
> doesn't sound very elegant (and not sure if it would be a valid solution).
> A better solution could be to add generics to the class, breaking the current
> contract (i.e. not allowing three types, boxing to longs, etc), but on the
> bright side, it won't use CCE as a normal workflow, nor need suppress
> warnings annotations any more.
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